The present invention relates to a valve seat for a fuel injector which includes a deposit resistant material in areas on the valve seat where deposits detrimental to injector performance can form.
Fuel injectors are used in internal combustion engines to provide a measured amount of fuel to each combustion chamber. The tips of the injectors protrude into the combustion chamber, and are exposed to a high temperature atmosphere containing fuel and air. Fuel in the presence of air at elevated temperatures reacts with metal in the injector, typically stainless steel, which is used to form the injector tip. The product of this reaction is a hard residue adhering to all surfaces wet with fuel and exposed to elevated temperatures and air. These surfaces include critical surfaces such as the inside of the fuel orifice all the way up to the sealing band of the seat, including the transition cone. The deposits on these surfaces restrict flow and distort the pattern and atomization of the injector fuel spray, resulting in higher emissions and reduced running stability of the engine.
Although combustion systems have been designed to reduce tip temperatures and to provide a cleansing air flow across the injector tip, making conditions for deposit less than optimal, deposits still form on the injector tip due to the reaction of the fuel with the stainless steel of the tip.
It would be beneficial to develop an injector surface exposed to fuel and air at elevated temperatures which is constructed from a material which retards or prevents the formation of deposits on the surface.
Briefly, the present invention discloses a fuel injector having an inlet, an outlet, and a passageway providing a fuel flow conduit from the inlet to the outlet. The fuel injector comprises a needle and an injector seat assembly. The needle is positionable in the passageway between a first position occluding the passageway and a second position permitting fuel flow. The injector seat assembly includes an injector seat having a longitudinal seat channel and a longitudinal channel axis extending therethrough. The injector seat is constructed from a first material. An insert is fixedly inserted into the longitudinal seat channel. The insert has a longitudinal insert channel and a longitudinal insert channel axis extending along the longitudinal seat channel axis. The insert is constructed from a second material, different from the first material.
Additionally, the present invention discloses an injector seat assembly comprising an injector seat having a longitudinal seat channel and a longitudinal channel axis extending therethrough. The injector seat is constructed from a first material. An insert is fixedly inserted into the longitudinal seat channel. The insert has a longitudinal insert channel and a longitudinal insert channel axis extending along the longitudinal seat channel axis. The insert is constructed from a second material, different from the first material.
Further, the present invention discloses a method of manufacturing an injector seat assembly comprising providing a valve seat blank having a longitudinal seat channel extending therethrough; installing an insert into the longitudinal seat channel; and forming a longitudinal insert channel in the insert, the longitudinal insert channel being co-axial with the longitudinal seat channel.